Binaries have their library locations stripped

1. Build proton
2. Install to /usr/local
3. Run "proton"
-> Blows up, can't find its library

https://paste.apache.org/gd56

http://stackoverflow.com/questions/3352041/creating-binary-with-cmake-removes-runtime-path

The default behavior of cmake is in my opinion wrong, and we should use the fix mentioned in that stackoverflow discussion.